This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 11(1999)-317780 filed on Nov. 9, 1999, the entire content of which is incorporated herein by reference.
The present invention is generally directed to a sensor device. More particularly, the present invention pertains to a seat occupant sensor device for detecting a seated person on a vehicular seat.
Seat occupant sensor devices which detect a seated person on a vehicular seat and make it possible to instruct or remind the person to put on their seat belt are known. The pressure sensitive switches used as an essential component of the seat occupant sensor devices are generally divided into several types, including a linear type using piezoelectric film, a film-using ON-OFF type, a limit switch using type, a magnet type using a strain gauge for detecting magnetic change.
The present invention is directed to a seat occupant sensor device that includes a pressure sensitive switch of film-using on-off type. The basic concept of the seat occupant sensor device of the type is disclosed in U.S. Pat. No. 5,896,090 granted to Okada et al.
The aforementioned basic concept has been employed to provide a seat occupant sensor device of the film-using type which is in the form of a pressure sensitive sensor device. This device includes, as shown in FIG. 11, a pair of bifurcated sensor portions 10 and a connecting portion 9 which terminates in a connector 11 to be electrically coupled to a vehicular harness. The sensor portions 10 are placed below the outer surface layer of the seat cushion and the connecting portion 9 extends from the rear portion of the seat cushion into the bottom portion of the seat cushion.
As can be seen from FIGS. 12 and 13, the structure of the sensor portion 10 and the connecting portion 9 includes a pair of opposed films 2 and 3 between which is positioned a spacer 1. The spacer 1 includes a plurality of openings 7 connected by a passage 6. A plurality of spaced circular electrodes 5 are provided on the inner surface of the film 2. The spaced circular electrodes 5 are formed along a single or common printed conductive path 4 of carbon or copper powder. The inner surface of the other film 3 is similarly provided with a plurality of spaced circular electrodes 5 formed along a single or common printed conductive path 4 of carbon or copper powder in the form of a carbon-printed strip or a copper-printed strip. Each of the electrodes 5 on the film 2 and the corresponding circular electrodes 5 positioned in opposing relation on the film 3 constitute a plurality of parallel arranged switches between the conductive paths 4, 4.
As best shown in FIG. 13, the conductive path 4 printed on the film 2 and the conductive path 4 printed on the film 3 are arranged in a horizontally symmetrical fashion with respect to the vertically extending air passage 6 which is formed in the spacer 1. One of the openings 7 in the spacer 1 is positioned between each of the circular electrodes 5 on the film 2 and the corresponding opposed circular electrode 5 on the film 3. When the seat is occupied by an individual, an electric connection or contact is established between the opposed circular electrodes 5, 5. Electric current thus flows through the conductive paths 4, 4, resulting in a detection of a person seated on the seat cushion.
Referring back to FIG. 11, the integrated structure of the films 2, 3 between which the foregoing arrangements are provided possesses a substantially Y-shaped configuration, in plan view, which includes the connecting portion 9 whose distal end is connected with a connector 11 and the pair of the sensor portions 10, 10 extending from the proximate end of the connecting portion 9. The connector 11 is connected to the conductive paths.
In addition, due to the fact that the integral structure of the sensor portions 10, 10 and the connecting portion 9 can be made when connecting the opposed films 2, 3 which are identical in shape through use of a bonding agent 8, as can be understood from the illustration in FIG. 13, each of the films 2, 3 can be obtained by punching a resin-made sheet provided with the plurality of printed circular electrodes 5 and the conductive path 4 into a predetermined shape. Such a formation process is technically advantageous in addition to the above-described configuration in which the sensor portions 10 together with the conductive path 4 extend from the connection portion 9 in a bifurcated fashion depending on the shape or dimension of seat cushion.
However, in the known sensor device described above, the yield rate in producing the films from a sheet of resin material is not very high.
Thus, a need exists to provide a seat occupant sensor device in which the film is formed into a shape which increases its yield rate when punched from a resin-made sheet and which is capable of being equipped in various types of vehicular seats, while at the same time maintaining the advantages mentioned above.
Generally speaking, the present invention provides a seat occupant sensor device in which a sheet of resin material on which a plurality of electrodes and a conductive path are printed is punched to form a film used in forming a pressure sensitive switch that includes a connecting portion positioned between a pair of sensor portions. When used, the connecting portion is brought into reversely bent position in which the connecting portion is bent rearwardly relative to the sensor portions through an angle of about 180 degrees.
One aspect of the present invention involves a seat occupant sensor device that includes a pressure sensitive switch having a pair of sensor portions and a connecting portion, each of the sensor portions being formed as an integration of a pair of opposed films and a spacer, with one of the films having disposed thereon a plurality of spaced first electrodes which are electrically connected to each other by way of a first conductive path and the other film having disposed thereon a plurality of spaced second electrodes which are electrically connected to each other by way of a second conductive path. The spacer is disposed between the pair of opposed films in such a manner that each of the first electrodes is maintained separate from the corresponding second electrode when the seat is unoccupied. The first conductive path and the second conductive path extend into the connecting portion, and the connecting portion is positioned, when in its free state, between the pair of sensor portions. A connector is provided at a distal end of the connecting portion for connecting the first conductive path and the second conductive path to an external control device. A block member is provided at a connecting region at which the proximate end of the connecting portion is connected to each of the sensor portions. The block member guides the connecting portion reversely.
According to another aspect of the invention, a seat occupant sensor device for detecting whether or not an occupant is seated on a seat includes a pressure sensitive switch comprised of a pair of films and a spacer positioned between the films, with one of the films being provided with a first electrode connected to a first conductive path and the other film being provided with a second electrode connected to a second conductive path. The spacer is disposed between the pair of films in such a manner that the first electrode is separate from the second electrode when the seat is unoccupied. The pressure switch possesses a configuration defining spaced part sensor portions and a connecting portion, with the first conductive path and the second conductive path extending into the connecting portion of the pressure sensitive switch, and with the sensor portions being connected to the connecting portion at a connecting region. A connector is connected to the connecting portion for connecting the first conductive path and the second conductive path to an external control device. A block member is positioned at the connecting region of the pressure sensitive switch with at least a part of the connecting portion extending along the block member in a direction generally opposite the sensor portions.
Another aspect of the invention involves a seat occupant sensor device that includes a pressure sensitive switch comprised of a pair of sensor portions, a connecting portion and a connecting region at which the connecting portion is integrated with the sensor portions. Each of the sensor portions is provided with at least one first electrode and at least one second electrode that are separated from one another when the seat is unoccupied and that contact one another when the seat is occupied. The first electrode of at least one sensor portion is connected to a first conductive path and the second electrode of at least one sensor portion is connected to a second conductive path, with the first and second conductive paths extending into the connecting portion. A connector is connected to the first conductive path and the second conductive path to connect the first and second conductive paths to an external control device. The connecting portion is bent back upon the connecting region and extends in a direction generally opposite the direction of extent of the sensor portions.